Piston Pump for Thick Materials

ABSTRACT

The invention relates to a multi-cylinder thick matter pump ( 1 ) which is used to continuously deliver especially concrete. Said thick matter pump comprises at least two delivery cylinders ( 3, 5 ) which transport the thick matter from a prefill tank ( 7 ) into a delivery pipe and a reversing valve ( 9 ) for alternately linking the delivery cylinders with the delivery pipe. The invention is characterized in that the reversing valve ( 9 ) comprises two pilot valves ( 15, 17 ) which can be displaced in a substantially translatory manner. Every pilot valve ( 15, 17 ) comprises a straight pipe section ( 15 L,  17 L) for linking the respective assigned delivery cylinder ( 3, 5 ) with the delivery pipe. Said pipe section can be linked with a manifold ( 19 ) in a pipe position downstream of the delivery cylinder. The invention also relates to a method for operating the inventive thick matter pump for continuous delivery.

The present invention regards a pump for thick materials with featuresaccording to the non characterizing part of patent claim 1. In a broadersense it also regards the controls of such thick materials pumps.

Thick materials piston pumps have been used for a long time inparticular at construction sites to feed concrete. Usually they areprovided as hydraulically operated piston pumps, mostly with twocylinders, feeding concrete through hoses or pipes. Subsequently, in asimplified manner, concrete feeding is being referred to. The inventionis not limited to an application with concrete feeding pumps but can beused for all similar thick materials pumps.

Such pumps have to fill a single feed line with two alternatively filledcylinders and associated pistons. The respectively filled cylinder isbeing connected with the feed line via a moveable pipe switch.Subsequently the piston pushes out the concrete (pump stroke), while theparallel piston is being retracted, in order to fill the cylinder withconcrete again (suction stroke). At the end of each stroke the movingdirection of the cylinder pistons is reversed and the pipe switch isshifted, so that pump strokes and suction strokes alternatecontinuously. The two pump pistons are preferably driven hydraulicallycoupled amongst each other, so that they basically work in acounteracting manner.

Common pipe switches (DE 29 33 128 C2) are arranged, so that they can beswitched back and forth between two end positions, wherein theyalternatively establish the connection between the cylinder openings andthe feed line on the one hand, and the pre filling container on theother hand. From this results a discontinuous feeding.

U.S. Pat. No. 3,663,129 describe a concrete pump with continuousfeeding, wherein the shift valve or its pipe switch consists of a socalled sleeve slide. Its waist opening is continuously but pivotallyconnected with the mouth of the feed pipe as a downstream outlet. Itskidney shaped inseam opening (inlet, upstream) is long enough to coverthe openings of both pump cylinders simultaneously. During the operationthe pipe switch performs a continuously oscillating pivoting motion,whose axis is coaxial with the mouth of the feed pipe. The pivotingangle of the pipe switch is approximately 50° towards both sides fromthe middle.

The pistons of the pump cylinders are controlled depending on themomentary position of the pipe switch, so that in the moment when bothcylinder openings are covered by the sleeve opening, one cylinder is atthe end, and the other cylinder is at the beginning of a pump stroke.Thereby the feeding action continuously shifts from one cylinder to theother. In the state of the art control system for the suction stroke andfor the pump stroke of each cylinder the same time span is used.Therefore there is no simultaneous feeding of both cylinders.

Due to the one sided bearing of the state of the art pipe switch on theside of the feed pipe and due to the enveloping support and sealingsurfaces only surrounding the sleeve opening, the substantial tiltingmoments of the state of the art design can not be completely received.It can not be excluded, that due to gap formation substantial leakinglosses occur in the seal area between the sleeve opening of the pipeswitch and the feeding cylinders, which in turn denies the realizationof a really continuous feed action.

The British Patent 1,063,020, as a gender defining state of the artdescribes a multi cylinder thick materials and concrete pump, whoseshift valve in one embodiment comprises two rotating slides, (alsoformed as sleeve valves), each controlled by a lifting cylinder of theirown. Their outlet ports are connected with a common Y-tube, which inturn is connected to the feed line downstream. Each rotating slide caneither work together with a single, or with two pump cylinders. Thoughsynchronous control of the rotating slides is mentioned, however withthis state of the art pump and control system continuous feeding of thefeeding cylinder into the common feed line is neither intended norpossible.

DE 30 06 542 C2 describes a guillotine flat valve for two cylinder thickmaterials pumps. It comprises a guillotine flap solidly connected with acontrol rod, which can be alternately moved back and forth between twoend positions in a guide housing or -frame. This state of the art 2/2way guillotine valve can also be installed between the flanges of aY-tube and an intake or exhaust tube. In concrete pumps it is preferablyinstalled between the bottom of a prefilling container and the exhaustpipes of a two-cylinder piston pump and/or the feed line and the exhaustpipes.

Furthermore it is also state of the art, to provide thick materialspumps of the kind that is being discussed here, with an insertionstation, through which a cleaning body for removing unused thickmaterials, which have remained in the feed line, can be inserted. Thisinsertion station comprises e.g. a chamber slide, moveable by a motor orhydraulically, with at least two chambers of equal cross section. In theresting position of the insertion station the one chamber forms asection of the feed line, while the other chamber is freely accessible.Into the latter the said cleaning body can be manually inserted from theoutside. For a cleaning procedure, with the thick materials pump shutdown, the insertion station is shifted into a working position, whereinthe chamber containing the cleaning body replaces the other chamberwithin the feed line. Then the cleaning body can be pressed through thefeed line with compressed air, whereby it pushes the thick materialahead of itself. These state of the art insertion stations, however haveto be provided in addition to the shift valve discussed above.

The objective of the invention is to provide an improved thick materialspump and a process for controlling a thick materials pump withcontinuous feeding.

This objective is accomplished according to the invention with thefeatures of patent claim one, with respect to the control process withthe features of the independent claim 19.

The features of the dependent claims associated with the independentclaims provide advantageous improvements of the invention.

While with the pumps according to the above explained U.S. and GBpatents the control slides are mostly located at the thick materialscontainer in an exposed manner, through providing the shift valve withtwo translatorically movable, in particular linear guided controlslides, an embodiment, less exposed to the thick material especially tothe concrete, can be created for the preferred application. On the onehand this is valid for abrasive uses, but also for loading throughdynamic pressure in the feed line or in the feeding cylinders. In thearea of the control slides the thick material is, different from theknown sleeve slides, not redirected under pressure, but substantiallyrun through the tubing sections in a straight manner. Only in thecollector tube (also Y-tube) the concrete flows from the feedingcylinders are merged. This substantially contributes to the pressurerelief of the slides themselves and does not only reduce the loads onthe bearings, but also reduces the frictional forces when switching thecontrol slides. Consequently this engineering solution noticeablyreduces mechanical wear of the moveable and non moveable parts of theshift valve.

It should be noted that, though a two cylinder thick materials pump isdiscussed here in an a preferred embodiment, the design according to theinvention can also be transposed to pumps with three or more cylinders,wherein a control slide would have to be associated with each feedingcylinder.

It is not absolutely necessary to guide the control slides in an exactlylinear manner, but according to the invention a slight arc can beprovided, whereby the major part of the motion remains translatoric.

Though it is conceivable to support the parallel control slides directlyat the surfaces facing each other, preferably however the guidancestructure for each control slide will have a dedicated slide railallowing larger offsets of the control slides during their operationalcycles.

For providing the shift valve (guidance structure and control slide)with sliding guides with friction and abrasion resistant materials andpossibly with wear parts known means can be applied, so this does notneed to be discussed in detail. The same applies for the seals betweenthe control slides and the openings of the feeding cylinders and thecollector tube.

According to the invention it is advantageous, when the control slidescan occupy three different positions, a transfer position, a blockingposition and an inlet position. To these three positions corresponds adesign or a subdivision of the control slides into three differentsections, this means a transfer section, a blocking section and an inletsection. The names of the sections or positions are self explanatory andwill be discussed in connection with the description of the attachedfigures.

It is advantageously possible to provide/prefabricate the abovementioned sections as single modules and assemble them in the requiredorder. Overall a control box or a control cage with the necessary valvetravel or functions is created. This design can favor the simplereplacement of single, prematurely worn or damaged sections, inparticular when connections are provided amongst them, that can bedisassembled.

It is understood that the two control slides are advantageously providedidentical amongst each other; variations can result from spaceconstraints, when attaching the respective drive systems.

A substantial advantage of the solution according to the invention isthe simply applicable option to use at least one, possibly both controlslides of the shift valve also as insertion station(s) for the cleaningbodies. The short tubing sections of the control slides and the feedline have to be cleaned during operation shut down of the pump, thismeans residual thick material or concrete leftovers have to be removed.

For this purpose the invention provides access to the control slides.This can be provided e.g. through flaps, which are normally closed, butprovide access to the control slides after opening.

For this a separate cleaning- or insertion position of the controlslide(s) can be provided. According to an advantageous refinement,however the inlet position of the control slide is used as insertionposition for the cleaning bodies at the same time. This is possible,because in this inlet position the tubing cross section of the controlslides is without function and also without pressure.

Based on the state of the art initially discussed such a combination isneither provided, nor easily possible.

As drives for the control slides preferably hydraulic positioningcylinders are used. However other suitable drives, e.g. electric motors,linear gear drives, etc. can be used.

In a first practical embodiment two serially coupled (working both ways)lifting cylinders can be used. In this configuration the stroke of eachof the cylinders corresponds to the shifting distance of the associatedcontrol slide from one position into the next. When both cylinders arecompletely retracted, the control slide is in its lowest position (e.g.inlet position). When a cylinder is extended, the control slide movesinto its middle position (e.g. blocking position). When also the secondcylinder is being fully extended the control slide reaches its topposition (e.g. the transfer position).

It is understood that the same effect can also be accomplished with atwo stage lifting cylinder (telescoping cylinder), whereby its middleposition, however has to be exactly controllable and lockable, in orderto assure defined shifting positions of the control slides.

Besides locking the respective positions of the control slides directlyand only through their drives, dedicated locking mechanisms certainlycan also be provided, preferably engaging directly between the guidancestructure and the control slides. These locking mechanisms can also beoperated remotely, this means engaged and disengaged. Furthermore it isalso conceivable to spring load such locking mechanisms in lockingdirection, so that they lock by themselves when the control slide movesinto the position to be fixated.

In case the above mentioned drive lifting cylinders are not to belocated coaxial with the control slides, e.g. because of spaceconstraints, they can be located parallel next to the control slides. Inthis case a load transfer in a perpendicular direction between thecontrol slides and the rod end pieces of the lifting cylinders has to beprovided, e.g. a cross beam or a console. For this a respective openingin the guidance structure for the control slides must be provided, so itcan follow the lateral movements of the slides.

Depending on the mounting conditions, the lifting cylinders can also belocated at an angle relative to the control slides, if a suitable lever-or angular gear system can be installed for adjusting the respectivecontrol slide positions.

Further details and advantages become evident from the drawing of anembodiment and it's following detailed description.

In a highly simplified and purely schematic illustration it is shown in:

FIG. 1 a perspective view of the assembly of the thick materials pumpwith additional functional components;

FIG. 2 a cross section side view of the thick materials pump with amultiple control slide shift valve according to the invention;

FIG. 3 a cut view through the middle axis of the feeding cylinders ofthe thick materials pump according to FIG. 2 (line II-II) for emphasingthe location of the feeding cylinder, the shift valve and the collectortube;

FIG. 4 a frontal view, tilted by 90° relative to FIG. 2 (cut along theline III-III in FIG. 1) of the shift valve with two parallel controlslides;

FIG. 5 a time-distance-diagram of the phase shifted strokes of bothpistons of the thick materials pump relative to the respective positionsof the two control slides;

FIG. 6 a first drive variant for a control slide, comprising twohydraulic lift cylinders in tandem arrangement;

FIG. 7 a second drive variant for a control slide comprising atelescopic cylinder, extendable in two stages, and

FIG. 8 a third drive variant for a control slide comprising a singlelong stroke lifting cylinder

FIG. 1 shows the perspective outlines of a thick materials pump 1 withtwo parallel feeding cylinders 3 and 5, lying next to each other, aprefilling container 7, a shift valve 9, a collector- or Y-tube 19, aswell as a short section of a feed line. The shift valve is located in ahousing, or in a guidance structure 11, reaching through the bottom ofthe prefilling container 7. Close to the bottom of the guidancestructure, on the side facing the feeding cylinders 3 and 5, amaintenance flap 13 is provided. Above the prefilling container, like anexplosion drawing two control slides 15 and 17 are shown, which areintended for moveable insertion into the housing shaped guidancestructure 11 of the shift valve 9, forming its valve body. This will besubsequently explained in detail.

FIG. 2 only shows the feeding cylinder 3 of the thick materials pump 1,which is located in the front of this view, in the area of its open(exhaust) end. The associated piston is not shown. The second feedingcylinder 5 is located behind the feeding cylinder 3 and covered inviewing direction. It is visible again in FIG. 3 from the top. Bothpistons of the feeding cylinders 3 and 5 are driven independently fromeach other (preferably hydraulically) and can in principle operate atany relative position or velocity within the limitations of theirstrokes and their control systems. However it is also possible tooperate them in hydraulically coupled manner. Both cylinders and pistonshave the same diameter, e. g. 250 mm.

The funnel shaped prefilling container 7, of which only the lower part(bottom part) is visible, is open at the top and is bolted to the openends of both feeding cylinders 3 and 5. The thick material to besupplied by the thick material pump is poured into it from the top. Theopenings of both feeding cylinders 3 and 5 exit in the lower area of theprefilling container 7. Thereby a maximum filling level of thickmaterial remains above the cylinder openings when thick material issucked into the feeding cylinders.

In the bottom of the prefilling container 7 a shift valve designated 9in its entirety is located in a known manner. Only through this shiftvalve 9 the thick material reaches the feeding cylinders 3 and 5, andonly via this shift valve the feeding cylinders eject the thick materialinto the feed line, which is not shown, as will be described in detaillater.

The shift valve 9 comprises a nonmoving guidance structure 11, which ismounted solid to the prefilling container 7. It protrudes to a certainextent upwards into the prefilling container, and also reaches downwardsthrough its bottom.

It should be noted, that in this example only a vertical installation ofthe guidance structure is referenced. However this is not mandatory.

In principle the guidance structure 11 can be provided as an open frame,in particular shaped like a shelf. Preferably it is constructed as asubstantially closed box with several functional openings, which inparticular in its upper area which is located in the prefillingcontainer, is kept open far enough in order to provide an undisturbedinflow of the thick material to the shift valves, also directly at thebottom of the prefilling container. Thereby, besides an upper openingalso an open side, e.g. towards the feeding cylinders can beadvantageous, without thereby compromising the exact guidance of thecontrol slides in this area.

In the lower section of the guidance structure 11, outside theprefilling container 7 a flap 13 is located, which is normally closed.By opening the flap 13 access to the interior of the guidance structure11 is provided, which is shaped like a box or a housing in theembodiment shown.

The latter forms a linear guide for the two control slides 15 and 17(the latter is visible in FIGS. 1, 3 and 4, and FIG. 2, it is coveredhowever as well as the feeding cylinder 5). These provide the connectionbetween the feeding cylinders on the one hand and a collector tube 19 onthe one hand, and the feed line connecting to it, on the other hand,which is not shown here. The feed tube 19 and the beginning of the feedline preferably are at the same elevation as the axis of the feedingcylinders 3 and 5.

Since both control slides are preferably identical, subsequently thecontrol slide 15 is described in lieu in more detail in FIG. 2. Itssections starting with “15” are present at the control slide 17 in thesame manner.

The control slide 15 can be positioned within the guidance structure,relative to its longitudinal extension, in three different predefinedshifting positions; this is performed through a drive system which is tobe discussed later. It also comprises three different functionalsections. On top is the inlet section 15 E. It is open towards theprefilling container and towards the feeding cylinder 3, so it has anopening in the direction of its longitudinal axis and another oneperpendicular to it. For redirecting the thick material by 90° from theprefilling container into the feeding cylinder, a feed slide 15S, thismeans a spherically curved gutter section is inserted. Its free crosssection preferably corresponds approximately to the cross section of thefeeding cylinder 3 and preferably forms a (deflection) angle of 90°. Inits place an appropriately angled elbow tube, possibly with an inletthat is expanded like a funnel can be provided and integrated into thestructure of the control slide. This inlet section 15E becomesfunctional, when the control slide 15 within the guidance structure 11is positioned in its lowest position. At the same time the section 15Eis closed on the surface pointing away from the feeding cylinder 3,forming a sealing surface 15D towards the collector tube 19. Thereby itis accomplished, that in the inlet position of the control slide 15 noconnection exists to the collector tube, or that it remains closed alsorelative to the prefilling container 7. As will become clearer later,this enables a feed operation of the other respective feeding cylinderduring the refilling of the one feeding cylinder in the sense of acontinuous feed.

Below the inlet section 15E follows a locking- or blocking section 15Bof the control slide 15. This only has the purpose of blocking theconnection between the feeding cylinder and the collector tube 19,visible to the right of the shift valve, on both sides. When the controlslide is in the middle of its three positions, the blocking section 15Blies in front of the opening of the feeding cylinder. After filling withthick material it can perform a short pre compression stroke, in orderto adapt the pressure in the freshly filled in thick material to thepressure in the feed line, connected to the collector tube. At the sametime a reverse impact onto the pressure in the feed line is avoidedthrough the sealing surface 15D towards the collector tube 19.

The blocking section, which does not have any flow guiding function,will be kept as short as possible, provided that it assures a safeblockage of the feeding cylinders, also against a substantialprecompression pressure. An extension of a little more than 250 mm (alsoa little larger than the diameter of the feeding cylinders) should besufficient, with exact positioning capability furthermore provided.

At the very bottom in the control slide 15 lies a transfer section 15L,preferably comprising a short, in particular straight tube section, openon both sides having the same interior cross section as the feedingcylinder 3. This adaptation of the shape and size of the transfersection 1 5L can be seen well in FIG. 2, as well as in FIG. 3. Duringthe operation of the shift valve and of the thick material pump it isconstantly filled with thick material.

As mentioned above, the mentioned sections can be considered singlemodules, that can be prefabricated and assembled into a control slide.

Overall the control slides form a 3/3 way valve together with the inletslides, the openings of the feeding cylinders and the openings of thecollector tube as paths, and with the three above described positions.

In FIG. 3 on the right side the geometric layout of the intake section(here 17E) next to the gutter (17S) of the control slide (here 17) onthe feeding cylinder (here 5), as well as the position of the sealingsurface 17D in front of the opening of the collector tube 19 can berecognized. Here the thick material can flow from the prefillingcontainer 7 only via the slide 17S into the opening of the feedingcylinder 5; the same holds for the respective inlet position of thecontrol slide 15.

Here also the side walls 15W, 17W of the control slides can be seen.These can be completely closed and are preferably made from a suitableflat material. On the top and on the bottom between the respectivesections, cross members have to be provided between the side walls, inorder to unite these into a stiff box forming the frame for the sectionsand components of the control slides. This frame e.g. has in theembodiment shown a planform of approximately 300 mm by 300 mm and isapproximately 800-900 mm tall.

Thereby a width of approximately 300 mm is defined by the diameter ofthe feeding cylinder of 250 mm. The height is determined through thedesign of the control slide in 3 sections. The depth (dimension inlongitudinal direction of the feeding cylinder) given above also atapproximately 300 mm, can be adapted to the respective installationrequirements, in order to provide an inlet cross section as big aspossible for the slides, it should however not be smaller than the crosssection of the feeding cylinders themselves.

Furthermore FIG. 3 also shows some design details of the layout of theguidance structure 11, thus the side walls 11W and the middle rim 11M.These form guide surfaces or rails for the control slides 15 and 17. Thelayout of the details of the guide elements is subject to the choice ofappropriate and wear resistant materials and shapes through a personskilled in the art.

In this cut view the shape and the technical function of the collectortube 19 becomes more apparent. It is provided as a Y-tube in a knownmanner, whose two branches each are connected to a control slide 15 or17 and its “mouth” or intake flange 20 is directly connected to the feedline, which is not shown in more detail.

The free cross section of the feed line in the mouth area is smallerthan in the intake area towards the control slides.

The compactness of the set up due to the directly adjacent controlslides can be seen very well in FIG. 4. In this cut view of the guidancestructure 11, the control slides 15 and 17 positioned next to each otherat different elevations and of the prefilling container 7 it isemphasized, that the bottom of the latter is penetrated by the guidancestructure 11. Its bottom 11B is located by ⅔ of the height of thecontrol slides below the bottom of the prefilling container. The walls11W of the guidance structure and its middle rim are visible in theirfull extension; they are by about ⅔ longer than the control slides 15and 17 themselves.

It is not mandatory to provide the walls of the guidance structure in afully enclosed manner, if the guiding elements for the control slide donot require it. However, for safety reasons (penetration of foreignobjects, preventing people from reaching in unintentionally, etc.accident risks) it can be advantageous to keep them closed.

Also a bottom 11B of the guidance structure is shown here as closed.However it can be useful to provide it in a perforated manner, or with adump flap in order to drain water seeping in between the control slidesand the guidance structure and in order to avoid motion restricting airpockets during the downward travel of control slides.

The two feeding cylinders 3 and 5 are located longitudinally in viewingdirection, covered behind the guidance structure 11. The control slide15 is at the same elevation as in FIG. 2 and FIG. 3 this means in itsmaximum possible (transfer)-position. The control slide 17 is also shownin its inlet position according to FIG. 3, its lowest possible positionwithin the guidance structure 11.

Thereby, for the moment the transfer section of the control slide 15 ispositioned in front of the opening of the feeding cylinder 3 (locatedbehind it and covered up). The latter is momentarily connected with thecollector tube 19 and the feed line in a fluidic manner, so that it caneject the filled in and precompressed thick material.

On the other hand the inlet section 17E of the control slide 17 lies infront of the opening of the feeding cylinder 5, so that the feedingcylinder 5 is connected with the prefilling container 7, so it can berefilled.

In FIG. 5, which will be discussed later, this corresponds to the phase7 of the motion phases of the shift valve.

At the same time the transfer section 1 7L of the control slide 17, atits lowest position, is located at the elevation of the flap 13,indicated by a dashed circle (See FIG. 1). It should be noted in thiscontext that flaps 13 can be provided for each control slide 15 and 17,and that the flaps 13, due to the close vicinity of both control slidesin the guidance structure, can also form a common maintenance and dumpflap for both control slides 15 and 17. It would then certainly have tobe wide enough to provide unrestricted access (in particular forinserting cleaning bodies) into both control slides (or their respectivetubing section). Onto these flap(s) no pressure will be exerted duringnormal operation, so that they do not have to be very strong, or do nothave to be sealed in particular. However they should, as mentionedabove, be safely lockable against opening during the operation of theshift valve 9.

It is evident, that through locating the guidance structure 11 at theelevation of the bottom of the prefilling container 7, the advantage canbe reaped, that the respective inlet sections of the control slidesbridge an elevation difference of the thick materials flow bythemselves. As can be seen clearly in FIG. 2, the thick material flowsin from the top and downward following gravity, offset by the height ofthe inlet section (approximately 250-300 mm) sideways (after adeflection of 90° into the feeding cylinder. The real bottom of theprefilling container is therefore located slightly above the openings ofthe feeding cylinders 3 and 5, hereby basically the advantage of thestatic pressure in the area of the cylinder openings is used in order tofacilitate refilling and sucking in.

The respective middle position of the control slides (“blockingposition”) lies in the exact middle between the extreme positions of thecontrol slides 15 and 17, shown in FIG. 3. It can either be adjusted andfixated directly through the drives, or additional mechanical lockingdevices or rests for securing the shifting positions in a defined mannercan be provided as mentioned above. The latter however are not shownhere.

In FIG. 4 also drive variants mentioned above are shown in a highlyschematic manner. On the left, at the control slide 15 a tandem liftingcylinder assembly 21 is provided. Onto a fixed point 23 a first liftingcylinder 25 is mounted, whose rod end piece carries an additionallifting cylinder 27. The rod end piece of the latter is connectedthrough a console 29, which is only shown in principle, with the flatslide 15. Certainly in the guidance structure 11 a longitudinal openingis provided, wherein the console 29 is guided in a sliding manner. Bothlifting cylinders are provided in a double acting set up. The liftingcylinder 27 has to be provided with flexible feed lines.

Visibly both rod end pieces of the lifting cylinders 25 and 27 are fullyextended. Through reversing one of the rod end pieces, the control slide15 can initially be brought into its middle position (blockingposition). When also the second rod end piece is retracted, the controlslide reaches its lower position (inlet position). In reverse movingdirection the rod end pieces are then extended one after the other,whereby the strokes of the lifting cylinders 25 and 27, in a suitableset up, jointly define the positions of the flat slide exactly.

On the right side the drive of the flat slide 17 is alternativelyprovided as a double acting 2 stage telescopic cylinder 31. It isdirectly located between a fixed point 33 and a console 35, which isonly shown in principle, which is in turn is connected with the controlslide 17 in a solid manner. It is also moveable in the guidancestructure 11 through a longitudinal opening. Since the control slide 17is in its lowest (inlet -) position, also the lifting cylinder 31 isfully retracted. Through extending its rod end piece into a first stageor lifting position, it positions the control slide 17 in its blockingposition, in a second stage, through further extension of the rod endpiece, the control slide 17 reaches its transfer position.

Again, with reference to FIG. 2, it becomes apparent in connection withthe low position of the control slide 17 in FIG. 2, that after openingthe flap, or the flaps 13, thick material still remaining in the tubingsections 15L or 17L (the latter shown in dashed lines) can easily beremoved. During normal operation of the shift valve it is certainly notnecessary, since this relatively small amount, or column of thickmaterial is ejected again into the collector tube and into the feedline, with the next feed or ejection stroke.

Since the transfer section in this position is completely separated fromthe feed line, there is no elevated pressure in it. Besides that, itwill be assured through appropriate means, that the flap 13 can not beopened when the thick materials pump and the shift valve run during feedoperations and that the shift valve can not be shifted while the flap isopen.

After opening the flap 13 also a cleaning body 37 (also shown in FIG. 2in dashed lines) can be inserted into the transfer section 15L or 17L(which have been purged by hand in a suitable manner before). Afterclosing the flap 13 it can be moved in the transfer section throughswitching the control slide, between the openings of the respectivefeeding cylinder or the collector tube 19. Subsequently it is runthrough the collector tube and the feed lines e.g. through compressedair, which is provided through an in feed between the feeding cylinderand the control slide, which is not shown here, in order to purge theselines from remaining thick material.

Through a passage of a cleaning body through both branches of thecollector- or Y-tube 19, these two are also purged, whereby thethoroughness of the cleaning of the feed line can be increased throughdouble passage of a cleaning body (subsequently through both branches ofthe collector tube and then through the common feed line). It isunderstood, that for both processes the same cleaning body can be usedtwice, or different cleaning bodies can be used.

Through a suitable shape of the collector tube in the joint area and/orthrough simultaneous pressurization into both branches of the collectortube 19 it can be assured that the cleaning body does not get caught inthe collector tube branch, which has been cleared before, upon itssecond passage.

With reference to FIG. 5, a time-distance diagram of the feeding pistonsand the motion phases of the control slides 15 and 17 of the shift valve9, after introducing all major parts of the thick materials pump and itsperiphery, the feed process per se and the controls of the thickmaterials pump and its shift valve are explained and discussed indetail. The two pistons of the feeding cylinders 3 and 5 are onlyrepresented as reference numerals K3 & K5 at the beginning of therespective diagram line. The motion or motion cycle of the piston K3 isshown in a dashed line, the one of the piston K5 in a solid line.

The above mentioned motion phases of the shift valve, whose reducedschematic display corresponds to the view of FIG. 4 are numbered from 1through 8 and shown next to each other in a diagram plotted over time,and separated from each other through vertical lines.

In phase one both control slides 15 and 17 are in their “transferposition”, this means their transfer sections 15L and 17L are located infront of the openings of the feeding cylinders 3 and 5 at the same time(in the following also starting position). Both feeding cylinders 3 and5 are also connected to the collector tube 19 and the subsequent feedline. None of the feeding cylinders communicates with the pre fillingcontainer 7.

According to phase 1 of the diagram the piston K3 of the feedingcylinder 3 moves towards the end of a pumping stroke, while the pistonK5 of the (freshly filled) cylinder 5 just starts with a new pump strokeafter a pre compression. Both pistons are moved in parallel and in thesame direction at a relatively slow speed. This can be called“synchronous motion phase”.

Phase 2 is a transition of the feeding cylinder 3 between the pumpstroke and the intake stroke. The control slide 15 was—preferably afterstopping the piston K3—moved downward by half of its total stroke, whilethe control slide 17 remained stationary. The opening of the feedingcylinder 3 is tightly sealed by the blocking section 15B, its piston K3stops for a short time before changing its stroke direction (“transitionphase”). The feeding cylinder 3 is completely closed relative to thecollector tube 19. This in between- or blocking position of the controlslide 15 safely avoids any fluidic short cut between the one pumping andthe other intaking feeding cylinder.

During this relatively short phase the control slide 15 can move; or itcan be stopped temporarily, in case the blocking section 15 b, asdiscussed, is provided very short.

During this time the piston K5 continues to be within its pumpingstroke, as can also be seen in the diagram phase 2. But the slope of itsmotion is steeper now, this means its forward velocity is increased to anormal level (e. g. doubled), compared to the previous synchronous phase1. Thereby compared to phase 1 a continuous flow of thick material inthe feed line is assured.

Phase 3 shows the first extreme relative position of both controlslides. The control slide 15 was displaced downward by its total stroke(e.g. by a total of a little more than 500 mm). It is located in itsinlet position now; its slide 15S lies in front of the opening of thefeeding cylinder 3, at the same time the control slide 17 is still inits “transfer position”, still allowing a feed from the feeding cylinder5 into the feed line.

The diagram shows in phase 3, that the piston K5 still runs at fullspeed or with full pumping power, while the piston K3 performs an intakestroke, preferably with a soft start and finish, but overall with ahigher speed than in the pump stroke (“intake phase”). Through thenormal (weight -) pressure of the thick material in the prefillingcontainer and its hydro dynamically advantageous guides on the slide15S, the feeding cylinder 3 is filled in an optimal manner.

Also in this phase a temporary stop of the oscillating motion of thecontrol slide 15 can be advantageous, so that the total intake strokecan be performed with the feeding cylinder 3 completely open.

The position of the shift valve 9 in phase 4 of FIG. 5 corresponds tophase 2. The control slide 15 was lifted from its intake position by thefirst half of its stroke. Now, as can be seen from the diagram, thepiston K3 (locked solid again by the blocking section 15B of the controlslide 15) of the feeding cylinder 3, can pre compress the thick materialthrough a very short stroke, that has just been taken in with lowdensity, preferably to the current operating pressure in the feed line(“pre compression phase”). This is also recommended with respect togases taken in with the thick material (air bubbles) and with respect tothe counter pressure from the collector tube 19 and the feed line, inorder to avoid shocks in the system, when the cylinder opening in thefollowing phase is connected again from the transfer section 15L to thefeed stream. Also here the control slide can be stopped temporarily orat least slowed down.

The piston K5 just runs into the end phase of its pump stroke, stillwith full speed.

Phase 5 exactly corresponds to phase 1 with respect to the position ofthe shift valve 9 (starting position “synchronous phase”). Also thediagram shows in phase 5, that now the pistons K3 and K5, with exchangedroles (relative to phase 1) recommence their phase shifted operationwith simultaneous pump feeding at reduced speed. Now begins the motioncycle of the control slide 17.

Phase 6 is a mirror image of phase 2; now only piston K3 pumps at fullspeed, while the blocking section 17B of the control slide 17 tightlyseals the feeding cylinder 5 and its piston K5 rests according to thediagram phase 6. The control slide 17 is shifted downward by half of itstotal stroke.

Phase 7 is a mirror image of phase 3. As mentioned before, also FIG. 4shows this phase. The control slide 17 has reached its lowest position.The feeding cylinder 5 is being refilled. Its piston K5 returnsaccording to diagram phase 7 into its starting position and via theslide 17S thick material flows into the feeding cylinder 5. At the sametime the feeding cylinder 3 provides full pumping power, its piston K5is at full forward velocity.

In phase 8, which is a mirror image of phase 4, the piston K5 precompresses the newly filled in thick material, while the piston K3reaches the end phase of its pumping stroke. In the diagram a fulloperation cycle of the two cylinder thick material pump is nowcompleted, the further operation continues again with phase 1.

For emphasizing the velocities, pressures, and forces during theoperation of the thick materials pump at continuous feed, it should bementioned that the total course of the phases 1-8 occurs within only 6seconds, as it is shown through the labeled time axis below the diagram.Thereby the pistons of the feeding cylinders have to go through strokesof approximately one meter length, while the total strokes of thecontrol slides are in a range between 500 mm and 600 mm.

For further interpretation of the diagram of FIG. 5 it should initiallybe repeated, that in the phases 1 and 5 both pistons simultaneously pumpthick material into the collector tube 19 and into the feed line. Duringthese phases their velocities are adjusted relative to each other, sothat their total feed volume corresponds to the feed volume of onesingle piston at normal forward velocity. Thereby, together with the precompression phase of the newly starting piston, a practically shock freeconstant feed volume of the thick materials pump is accomplished.

In all other phases only one of the pistons is in pumping operation, andit then runs preferably at constant speed. The static pressure in therespective non moving branch of the collector tube 19 then correspondsto the pressure in the feed line. It is safely received by the sealingsurfaces 15D or 17D of the control slide in its blocking and/or inletposition.

The design of the shift valve according to the invention and a dedicatedforward motion control of the feeding pistons makes it possible toaccomplish a constant output of the thick materials pump in the phasesof the common pump strokes, compared to the single pumping power of apiston, and thereby practically eliminating the pulsation of the thickmaterials flow in the feed line. This is especially facilitated by thepre compression of the thick material in the phases 4 and 8, therebyavoiding the opening of a freshly filled feeding cylinder 3 or 5, orconnecting a pressure free (“buffer space”) with the feed line. Thevolume of the thick material in the “reactivated” transfer section 15Lor 17L is negligible with respect to such buffer effect.

Though, thru the pre compression steps (phases 4 and 8) considerableforces are imparted to the control slides 15 and 17, however they areeasily received and transferred through their robust and stillrelatively simple linear slide bearing within the guidance structure 11.Hereby also the advantage of a substantially translatoric slide bearingcomes to bear, as well as the advantage of a constant connection of thedown stream end of the collector tube 19 with the feed line.

In an advantageous manner the weight of the thick material can supportthe quick feed via the slide of the control slide towards the cylinderopening to be feed.

The momentary position of the pistons K3 and K5 and of the controlslides 15 and 17 can be sensed with suitable sensors (distance sensors,position sensors, pressure sensors), possibly directly at the respectivedrives. The sensors preferably provide their position signals to apreferably central control unit of the thick materials pump, which inturn controls the drives of the feeding pistons K3 and K5 and of theshift valve 9.

In particular, in moments of simultaneous feed from both feedingcylinders it controls the reduction of their forward velocities. Notnecessarily both pistons have to be controlled to half speed, but inprinciple one piston can be controlled to ⅓ of full velocity and theother one to ⅔ of full velocity (assuming equal diameters and totalstrokes). The goal remains a feed stream, as constant as possible, ofthick material in the feed line.

Furthermore the control unit has to, during the time span, when thefreshly filled feeding cylinder is locked by the blocking section of theassociated control slide 15 or 17, on the one hand stop the shift valveor adjust it to slower travel, on the other hand control the precompression stroke of the associated piston. This possibly requires anadditional pressure sensor that can be located in the cylinder in thepiston, or also in the pressurized branch of the collector tube 19. Ablocking of the control slides 15 and 17 through increased pressureduring pre compression can certainly be excluded through a pressurelimiter.

Also in other phases, e.g. the synchronous phases, the transition phaseand the inlet- or suction phase, a reduced speed of the control slides15/17 or even their momentary stand still between the reversal pointscan be advantageous. Overall one will have to carefully weigh betweenstand still times and motion times of the control slides, so that on theone hand the available flow cross sections are not reduced too muchthrough overlap of the blocking sections with the openings of thefeeding cylinders, on the other hand no excessive slide velocities arerequired.

For the continuous operation of the thick materials pump it can also behelpful to run through the various slide positions at constant speedwithout slowing down or stopping.

FIG. 6 once more addresses the control the slide drive 21 with tandemlift cylinders shown in FIG. 4 on the left in more detail. Again, onecan see the fixed point 23 provided with a joint (preferably at thehousing of the shift valve 9) and the lifting cylinders 25 and 27, botharranged in series on top of each other, as well as the console 29 forthe control slide, which is not shown here. The lifting cylinders 25 and27 are shown here in a schematic cut view so that three motion phases ofthis drive concept become apparent from the right to the left: on thevery left both lifting cylinders are loaded on their rod sides and arein their respective lowest position. Accordingly the control slide is inits inlet position. In the middle phase the lower lifting cylinder 25 isloaded on the piston side and is in its upper position, while the upperlifting cylinder which is moved along, is still loaded on the rod side(blocking position of the control slide). The third phase shows bothlifting cylinders in piston loaded, fully extended position (transferposition of the control slide). For lowering the latter the phases areperformed in reverse direction. With reference to the respective,previously discussed positions of the control bodies in the previousfigures the three phases in FIG. 6-8 are designated with the letters E(inlet position), B (blocking position) and L (transfer position).

FIG. 7 shows the same process with a two stage telescopic cylinder 31,as shown in FIG. 3 on the right side. The fixed point 33 which isattached to the housing of the shift valve 9 with a pivotable joint,carries the lifting cylinder, which is connected to a control slidethrough a console 35, with its rod. Again 3 working positions of thelifting cylinder 31 are provided, wherein for the middle position anadditional stop or blocking mechanism is provided, in order to make thisposition approachable in a defined manner. A hydraulic locking of thismiddle position directly in the lifting cylinder 31 could also berealized, but might not be adjustable exactly enough in demandingcontinuous operations. In practice a small lifting cylinder 39 isprovided here, which is mounted to the housing of the shift valve in asolid manner, possibly via an additional fixed console and whose rod endpiece can be extended into the travel of the telescopic cylinder 31.

In FIG. 7 one can see again from the left to the right, analogous toFIG. 6 three motion phases, or positions E, B and L. On the very leftthe telescopic cylinder is loaded on the rod side and is in its lowestposition. The blocking cylinder 39 is retracted. In the middle thetelescopic cylinder is semi extended; its rod end piece abuts to themeanwhile also extended rod end piece of the blocking cylinder 39, sothat here the intermediate position (blocking position) is reached. Inthe right phase the blocking cylinder 39 is retracted again, so that theway for the rod of the telescopic cylinder 31 into the upper most, fullyextended (stop -) position is free. Accordingly also the control slide(not shown) which is connected via the console, is now in its uppermost(transfer-) position L.

FIG. 8 shows an equivalent to FIG. 7, this means a two stagecontrollable long stroke lifting cylinder 41, associated with a blockingcylinder 43. The fixed point 33 and the console 35 are identical toFIGS. 6 and 7. Again, on the very left, the long stroke lifting cylinder41 is loaded on the rod side in its lowest possible position E. Theblocking cylinder 43 is retracted. During the transition of the liftingcylinder 41 (now loaded on the piston side) into its middle position (B)also the blocking cylinder 43 is extended, so that its rod end pieceenters into the path of the rod end piece of the lifting cylinder 41,blocking it in the middle position. On the very right in FIG. 8, theblocking cylinder 43 is retracted again and the rod of the liftingcylinder 41 can be extended in its uppermost position (L).

Also in the configurations according to FIGS. 7 and 8, certainly fordownward motion of the associated control slide, the reverse sequence ofthe previously discussed motion phases or positions is required, what isbeing controlled through rod side loading of the lifting cylinders.

It is understood that the blocking cylinders 39 and 43 with therespective lifting cylinders or rod end pieces have to be adjusted inany case in a manner, so that also during the upward travel of thelifting cylinders the middle position is exactly adjustable. Theschematically simplified arrangements shown in here only serve forbetter understanding of the working principle of these drives, but doreflect the real installation conditions and the cooperation between thelifting and blocking cylinders only on a limited basis.

1-33. (canceled)
 34. A multi cylinder thick materials pump for providingconcrete comprising: at least two feeding cylinders for feeding thickmaterial from a pre filling container into a feed line; a shift valvefor alternatively connecting the feeding cylinders with the feed lineassociated with it; the shift valve comprising at least two moveablevalve bodies, each body comprising a transfer section between each ofthe feeding cylinders and the feed line, the shift valve being connecteddownstream of the feeding cylinders to a collector tube, and the shiftvalve comprising two substantially translatorically movable controlslides, each slide including a straight transfer section for connectingeach of their associated feeding cylinders with the feed line and ablocking section blocking the connection.
 35. A thick materials pumpaccording to claim 34, wherein the shift valve includes a guidancestructure for the control slides, the guidance structure having openingsfor passing through thick materials flows.
 36. A thick materials pumpaccording to claim 35, further comprising a pre filling container, saidcontrol slides each having an inlet opening, and the guidance structurebeing mounted into the pre filling container in a fixed manner so thatthe control slides and their inlet openings are always in contact withthe thick material filled in.
 37. A thick materials pump according toclaim 35, wherein the guidance structure is substantially shaped as abox or a frame, the box or frame forming a separate guide for eachcontrol slide.
 38. A thick materials pump according to claim 34, whereinthe control slides can each be positioned within the guidance structurein at least two different positions, the two positions including atransfer position wherein the feeding cylinder can eject into thecollector tube, and a blocking- or inlet position wherein the feedingcylinder can suck thick material out of the pre filling container.
 39. Athick materials pump according to claim 34, wherein the control slidesare substantially identically.
 40. A thick materials pump according toclaim 34, wherein at least one of the control slides is divided intothree sections along its stroke, one of the three sections being thetransfer section and another of the three sections being an inletsection.
 41. A thick materials pump according to claim 40, wherein theblocking section is provided between the transfer section and the inletsection.
 42. A thick materials pump according to claim 40, wherein thesections of the control slides are provided as single modules andconnected to each other in a disconnectable manner.
 43. A thickmaterials pump according to claim 34, wherein the guidance structureincludes at least one flap for removing thick material from the transfersection of one of the control slides.
 44. A thick materials pumpaccording to claim 43, wherein the flap is a common flap for both of thecontrol slides.
 45. A thick materials pump according to claim 34,wherein the control slides are drivable and positionable independentlyfrom each other.
 46. A thick materials pump according to claim 45,further comprising a drive for the control slide, the drive including atandem lifting cylinder array within two serially connected liftingcylinders, each of the cylinders having a stroke corresponding to thetravel of the control slide from one position into a neighboringposition.
 47. A thick materials pump according to claim 45, furthercomprising a drive for the control slide, the drive including atelescoping lifting cylinder with two lifting stages, each of the stagesof the cylinders corresponding to the travel of the control slide fromone position into a neighboring position.
 48. A thick materials pumpaccording to claim 46, wherein the lifting cylinders are located inparallel next to the control slides, said cylinders being coupled withthe slides via consoles, and the guidance structure including thecontrol slide guides for the consoles.
 49. A thick materials pumpaccording to claim 34, wherein the transfer section of each controlslide comprises a cylindrical tube with the same diameter as the feedingcylinders.
 50. A thick materials pump according to claim 40, wherein arerouting system is provided in the inlet section of at least onecontrol slide.
 51. A thick materials pump according to claim 34, furthercomprising a control unit and position indicators, the positionindicators providing to the control unit momentary positions of theshift valve and the control slides as well as of the feeding pistons ofthe feeding cylinders, and the control unit controlling drives of thecontrol slides and of the feeding pistons according to a predeterminedtime distance pattern in a cyclical manner.
 52. A process for operatinga thick materials pump for continuous feeding comprising: providing athick materials pump, the pump comprising at least two open feedingcylinders with feeding pistons and a shift valve with control slides,which are controllable independently from each other and adapted to themotion of the feeding pistons, each control slide including at least onetransfer section for connecting an associated feeding cylinder with afeed line and an intake section for sucking in thick material from a prefilling container through the associated feeding cylinder; andcontrolling a synchronous travel phase of the feeding pistons in acyclical manner while its at least two control slides are located in atransfer position, wherein its transfer sections connect the associatedfeeding cylinders to the feed line for preliminary simultaneousexpulsion of thick material.
 53. A process according to claim 52,further comprising adjusting the feeding pistons in the synchronoustravel phase to each other, so that the thick materials quantity pumpedby the pistons simultaneously is approximately equal to feeding throughone piston alone during the suction stroke of the respective otherpiston.
 54. A process according to claim 52, further comprisingmomentarily closing the opening of each feed cylinder at the beginningof the pump stroke of each feeding piston of each feeding cylinderthrough the blocking section of the control slides.
 55. A processaccording to claim 54, further comprising providing each pump stroke ofa piston with a pre compression phase, a first synchronous phase, a pumpphase, and a second synchronous phase.
 56. A process according to claim52, further comprising driving both feeding pistons during thesynchronous travel phase at the same speed.
 57. A process according toclaim 52, wherein upon a pump stroke a transition phase with a standstill of a feeding piston during a continuing pump stroke of the otherfeeding piston follows.
 58. A process according to claim 52, wherein thesuction stroke of each piston is faster than its pump stroke, inparticular between a transition phase and a pre compression phase.
 59. Aprocess according to claim 58, further comprising providing each suctionstroke of a piston with a start ramp and a stop ramp with a reducedvelocity.
 60. A process according to claim 52, further comprisingslowing down or stopping momentarily the control slides during thesynchronous phases.
 61. A process according to claim 52, furthercomprising slowing down or stopping momentarily the control slides in apre compression phase.
 62. A process according to claim 52, furthercomprising slowing down or stopping momentarily the control slides in atransition phase.
 63. A process according to claim 52, furthercomprising slowing down or stopping momentarily the control slides in asuction phase.
 64. A process according to claim 52, further comprisingpositioning the control slides in an operating position in theoperational pauses of the thick materials pump, and allowing the removalof remaining thick material and the insertion of a cleaning body whenrequired.
 65. A process according claim 64, further comprising providingthe operational position at the inlet position of the control slide. 66.A process according to claim 64, further comprising providing a safetydevice for preventing the starting of the control slide, and activatingsaid safety device during the removal and/or insertion process.
 67. Aprocess according to claim 47, wherein the lifting cylinders are locatedin parallel next to the control slides, said cylinders being coupledwith the slides via consoles, and the guidance structure including thecontrol slide guides for the consoles.